Why get a full exhaust instead of a slip on?

[cerino2000]

Do the full exhaust kits make that much difference? Is their header design that much better over stock? I can see it in the muffler portion being different but not so sure about the full set up.

Also, do you have to re-jet when getting just a slip on?

[XXXRACER165]

The Header is better from some companies. But then again, HMF is claiming an impressive 8hp gain from only a slip-on. While my WB e-series full system says 8hp too. So pick carefully!

[Hondamaster5505]

8hp is bullsh*t

The most a system makes on a 400ex is like max 3hp and slip-ons are like 2hp.

8 my a**

Originally posted by XXXRACER165
The Header is better from some companies. But then again, HMF is claiming an impressive 8hp gain from only a slip-on. While my WB e-series full system says 8hp too. So pick carefully!

I would love to know where you are getting these numbers. White brother e-series says a 2-4HP gain and HMF says 4HP gain. Not even the full systems say that much, HMF full system is 6HP

[zrpilot]

Originally posted by cerino2000
Do the full exhaust kits make that much difference? Is their header design that much better over stock? I can see it in the muffler portion being different but not so sure about the full set up.

A full system will make a difference in most cases, but on a mostly stock engine, save your money and just use the slip-on.

Originally posted by cerino2000

Also, do you have to re-jet when getting just a slip on?


ABSOLUTELY!

[oleboy87]

and yea you will need to rejet...

stock 400ex headers where designed to be oversize than they needed to be so you could simple get a slip on and get good gains. Honda is smart and they know what they are doing, stocl header at the end is about 1.5" and the HMF full system is 2". Yes that is a big difference but for what its worth it would only be best on a modded engine. My friend had a 440 with just an HMF slip on and it hauled a**! In that situation the full system would be best on a modded engine. Stock engine you will most likely have less torque with the full system than the stock headers.

[mittman]

when i got my full yosh it said i didnt have to rejet but i did anyway

[XXXRACER165]

Originally posted by FoxHondaRider
I would love to know where you are getting these numbers. White brother e-series says a 2-4HP gain and HMF says 4HP gain. Not even the full systems say that much, HMF full system is 6HP

Go to the ebay store "ATV Galaxy" and find a HMF Ironman slip-on for a 400EX, click on it and read the item description. Says 8hp gain.

[XXXRACER165]

8 Horsepower Increase
HMF Ironman Pro Series
Slip-On Exhaust
Black Chrome Powdercoated Muffler
Free Shipping, Free Jets, & Free Spark Arrestor ($50 Value)
Honda 400EX (1999-2007)
(Please Specify Year When Ordering)
Part #NATH400EXSARC2.0

HMF Ironman Series exhaust system offers a broad power band and outstanding acceleration like no other exhaust system. This awesome power comes from intensive R&D to produce performance optimization.

[oleboy87]

atv galaxy is full of i don't go by anything they say it took them about 4 weeks to send me my slip on.. but i just did some reaserch and this is what i found dont know if its true or not...

http://hmfengineering.com/forums/showthread.php?t=57

[XXXRACER165]

Yeah Thats more like it. I didn't believe it either.

[oleboy87]

yeeaa but even though hmf says that im kinda skeptical about going by what they say.. they give out false info

[NJ450rider]

IF the internals of your 400ex are stock or mild(like cam, air filter etc) all you will need is a slip on. a full system is needed for big mods like piston/cam/bigger carb, bigbores etc. The most youll see from a slip on is 4-6 hp max and thats it. Whatever any company tells you there full of sh*t and thats it. And getting an hmf ironman slipon over say an hmf sport slipon is stupid. your gonna see the same hp numbers. only the ironman slipon being super loud and i would know i have one on my 450r. its super loud. Just like a car or truck theres such thing as too big an exhaust system. no back pressure is a bad thing! youll lose hp!

mobile dyno did dyno test with a stock 400ex, then with a HMF slip on then with a white Brother e-series full system and the HMF was still on top. Yes a $220 exhaust gave more HP than a $500 full system. There was a whole thread about it with the graphs and all

[XXXRACER165]

Originally posted by FoxHondaRider
mobile dyno did dyno test with a stock 400ex, then with a HMF slip on then with a white Brother e-series full system and the HMF was still on top. Yes a $220 exhaust gave more HP than a $500 full system. There was a whole thread about it with the graphs and all


But on a 440 the full system will make more juice

[NJ450rider]

YES you need a full system on a big bore engine!!! Look at it this way an engine is like a big vacuum. More air into a bigger chamber(big bore/higher compression) needs more air out to make more power. If you have lots of air going into a small chamber(stock cylinder/compression) and a bigger exhaust your not gonna make more power because the chamber is too small. there has to be a balance of air in and out. That way optimal power is made.

The same goes for stock intake/carb going into a stock cylinder/compression ratio with a full exhaust. optimal power isnt going to be made because theres not enough air coming into the chamber(think vacuum) for the big exhaust system to have full potential. This isnt hard people its basic engine knowledge!


This is another reason why a big cam isnt needed if you dont have alot of engine mods and head work. It all goes back to the vacuum idea.

[red_rider_069]

Originally posted by NJ450rider
YES you need a full system on a big bore engine!!! Look at it this way an engine is like a big vacuum. More air into a bigger chamber(big bore/higher compression) needs more air out to make more power. If you have lots of air going into a small chamber(stock cylinder/compression) and a bigger exhaust your not gonna make more power because the chamber is too small. there has to be a balance of air in and out. That way optimal power is made.

The same goes for stock intake/carb going into a stock cylinder/compression ratio with a full exhaust. optimal power isnt going to be made because theres not enough air coming into the chamber(think vacuum) for the big exhaust system to have full potential. This isnt hard people its basic engine knowledge!


This is another reason why a big cam isnt needed if you dont have alot of engine mods and head work. It all goes back to the vacuum idea.
ACTUALLY NORE YOU DONT.. YOU CAN RUN A BIG BORE 440 OFF STOCK EXHAUST AND IT RUNS GOOD.. AND I WOULD GET HEADER.. THICKERS HEAD PORTS :D MORE NOISE.. MORE AIR FLOW THINK ABOUT IT.. AND YEA YOU GOT TO JET WHEN YOU GET A SLIP ON IF YOU ARE RUNNING IT WITH K&N OR ANY AIR FILTER WITH OUT THE AIRBOX LID.. WITH THE LID YOU CAN RUN IT STOCK JET.. MORE JUICE OUT OF AFTER MARKET PARTS W/O LID AND JETS!.. SOMEONE QUIOT ME IF IM WRONG:D

[Ruby Soho]

you dont NEED a full for a bigbore

i have a stock exhaust currently, and it runs good.

slipon will do you fine

[XXXRACER165]

You need a full system to get the most juice from a 440. Proven FACT!

[red_rider_069]

yea.. more juice with full exhaust.. but rider has a lot to do aswell.. so dont worry about bb and a slip on if you rip:cool: